The fabrication process of a InP-based two-dimensional photonic crystal membrane structure is developed. The process includes a well-calibrated electron-beam (e-beam) lithography and InGaAsP/InP etching using methane-hydrogen-argon reactive ion etching. The photonic crystal blocks with ten rows of a hexagonal array of holes with various lattice constants and filling factors are successfully fabricated and characterized by optical transmission measurement. The sensitivity of the band gap to the systematic fabrication error is determined. (C) 2004 American Vacuum Society.